System for feeding back index of codeword matrix

Abstract

A system is provided for performing downlink beamforming based on information fed back by a mobile station. The mobile station includes a channel matrix generation unit to generate a channel matrix with respect to channels ranging from a base station to a mobile station, the base station including multiple transmission antennas, a codebook updating unit to generate a second codebook including a plurality of second codeword matrixes based on the generated channel matrix and a first codebook including a plurality of first codeword matrixes, a codeword selection unit to select at least one transmission codeword matrix from among the plurality of second codeword matrixes, a transmission unit to transmit an index of the selected transmission codeword matrix to the base station, and a receiving unit to receive data transmitted from the base station via the multiple transmission antennas.

1. A mobile station comprising:
 a channel matrix generation unit configured to generate a channel matrix with respect to channels ranging from a base station to a mobile station, the base station including multiple transmission antennas; 
 a codebook updating unit configured to generate a second codebook including a plurality of second codeword matrixes based on 1) the generated channel matrix and 2) a first codebook including a plurality of first codeword matrixes; 
 a codeword selection unit configured to select at least one transmission codeword matrix from among the plurality of second codeword matrixes; 
 a transmission unit configured to transmit an index of the selected transmission codeword matrix to the base station; and 
 a receiving unit configured to receive data transmitted from the base station via the multiple transmission antennas based on the transmitted index, wherein the channel matrix generation unit, the codebook updating unit, the codeword selection unit, the transmission unit, the receiving unit or any combination thereof is implemented by hardware. 
 
     
     
       2. The mobile station of  claim 1 , wherein the channel matrix generation unit generates the channel matrix for each time interval having a predetermined length, and the mobile station further comprises:
 a time correlation coefficient-generation unit configured to generate a time correlation coefficient by comparing a first channel matrix generated in a specific time interval and a second channel matrix generated in another time interval adjacent to the specific time interval, 
 wherein the codebook updating unit generates the second codebook based on the time correlation coefficient. 
 
     
     
       3. The mobile station of  claim 2 , wherein the transmission unit transmits the generated time correlation coefficient to the base station, and the receiving unit receives the data transmitted from the base station according to the transmitted time correlation coefficient. 
     
     
       4. The mobile station of  claim 2 , wherein the codebook updating unit generates a first time correlation coefficient during the specific time interval and a second time correlation coefficient during a time interval adjacent to the specific time interval, and generates the second codebook based on a compared result between the first and second time correlation coefficients. 
     
     
       5. The mobile station of  claim 2 , further comprising:
 a codebook change unit configured to generate a third codeword matrix with respect to each of the plurality of first codeword matrixes based on the time correlation coefficient and an identity matrix, 
 wherein the codebook updating unit generates the second codeword matrix based on a singular value decomposition result with respect to the third codeword matrix. 
 
     
     
       6. The mobile station of  claim 2 , further comprising:
 a codebook change unit configured to generate a third codeword matrix with respect to each of the plurality of first codeword matrixes based on the time correlation coefficient and an identity matrix, 
 wherein the codebook updating unit generates the plurality of second codeword matrixes based on a reverse matrix of the third codeword matrix. 
 
     
     
       7. The mobile station of  claim 1 , further comprising:
 a precoding matrix-generation unit configured to generate a plurality of second precoding matrixes by multiplying a first precoding matrix associated with the base station by each of the plurality of second codeword matrixes, 
 wherein the codeword selection unit selects the transmission codeword matrix based on the generated second precoding matrixes. 
 
     
     
       8. The mobile station of  claim 7 , further comprising:
 an auto correlation matrix generation unit configured to generate an auto-correlation matrix associated with the channel based on the channel matrix; and 
 an eigenvalue-decomposition unit configured to perform an eigenvalue decomposition with respect to the auto-correlation matrix, 
 wherein the first precoding matrix is determined based on a result of the eigenvalue decomposition performed with respect to the auto-correlation matrix. 
 
     
     
       9. The mobile station of  claim 7 , further comprising:
 a transmission rate computation unit configured to compute a transmission rate of data transmitted to the mobile station via the multiple transmission antennas with respect to each of the plurality of second precoding matrixes, 
 wherein the codeword selection unit selects the transmission codeword matrix based on the second precoding matrix maximizing the transmission rate. 
 
     
     
       10. The mobile station of  claim 9 , further comprising:
 a precoding matrix updating unit configured to update the first precoding matrix based on the second precoding matrix maximizing the transmission rate. 
 
     
     
       11. The mobile station of  claim 2 , further comprising:
 a candidate channel matrix generation unit configured to generate a plurality of candidate channel matrixes by multiplying the second channel matrix by each of the plurality of second codeword matrixes; and 
 a candidate channel vector-selection unit configured to select a candidate channel matrix having the smallest difference with the first channel matrix, 
 wherein the codeword selection unit selects the transmission codeword matrix based on the selected candidate channel matrix. 
 
     
     
       12. The mobile station of  claim 1 , wherein the first codeword matrixes are equally spaced in a matrix space. 
     
     
       13. A base station device, comprising:
 a transmission unit to include multiple transmission antennas; 
 a codebook updating unit to generate a second codebook including a plurality of second codeword matrixes based on 1) a channel matrix with respect to channels ranging from the multiple transmission antennas to a mobile station connected with the base station and 2) a first codebook including a plurality of first codeword matrixes; 
 a receiving unit to receive, from the mobile station, an index of at least one codeword matrix from among the plurality of second codeword matrixes; and 
 a transmission unit to transmit data to the mobile station via the multiple transmission antennas based on the second codeword matrix corresponding to the received index. 
 
     
     
       14. The base station device of  claim 13 , wherein the transmission unit transmits a plurality of pilot signals to the mobile station via each of the multiple transmission antennas, and the channel matrix is generated based on the pilot signal. 
     
     
       15. The base station device of  claim 13 , wherein the receiving unit receives, from the mobile station, a time correlation coefficient related with occurrence/nonoccurrence of a change in the channel matrix. 
     
     
       16. The base station device of  claim 15 , further comprising:
 a codebook change unit to generate a third codeword matrix with respect to each of the plurality of first codeword matrixes based on the time correlation coefficient and an identity matrix, 
 wherein the codebook updating unit generates the second codeword matrix based on a result of a singular value decomposition performed with respect to the third codeword matrix. 
 
     
     
       17. The base station device of  claim 15 , further comprising:
 a codebook change unit to generate a third codeword matrix with respect to each of the plurality of first codeword matrixes based on the time correlation coefficient and an identity matrix, 
 wherein the codebook updating unit generates the second codeword matrix based on a reverse matrix of the third codeword matrix. 
 
     
     
       18. The base station device of  claim 13 , further comprising:
 a channel matrix updating unit to update the channel matrix by multiplying the channel matrix and the second codeword matrix corresponding to the received index, wherein the transmission unit transmits data to the mobile station based on the updated channel matrix.